'Dexter', 'Mad Men' episodes leaked

Episodes of AMC's Mad Men and Showtime's Dexter have been leaked online ahead of their television premieres.

The season four premiere of serial killer-themed Dexter has popped up in several internet locations and is yet to be removed, while the Mad Men episode was put on to iTunes by mistake, but has since been rectified, says The Hollywood Reporter.

The episode, scheduled to air tonight, was apparently made available briefly on Tuesday evening to holders of an iTunes Season Pass.

AMC said that it is investigating how the leak came about and has requested that people who have seen it refrain from spoiling it for fans who watch the show at regular pace.